What so the war was against some random monster invaders????
Where the fuck is the nuance then? How could there possibly be sympathizers?
What the fuck is samura being a crybaby bitch about?
No one was described as "random monster invaders". The only thing you could be making that assumption from is the panel of invaders being shown ominously in the distance with the flames/smoke/aura coming from one of them. But that isn't really something uniquely monstrous. Chihiro probably would have looked like that while using Enten if you zoomed out.
What we learn from this chapter is that a mysterious island, Shokoku, appeared with a supernatural material on it, the Datenseki. The inhabitants of this island can use this material safely. There was an invasion.
We also learn that there were sympathizers, and we have known that Samura, someone from the front lines, believes that all the sword bearers are more villains than heroes.
These ideas do not contradict each other. It just means there is more to the story than has been revealed, so there's your nuance.